著者

天野 和孝 菅野 三郎

出版者

日本古生物学会

雑誌

化石 (ISSN:00229202)

巻号頁・発行日

no.51, pp.1-14, 1991-11-30

被引用文献数

8

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In the western part of Joetsu City, the Pliocene strata are subdivided into the Kawazume, Nadachi and Tanihama formations in upward sequence. The following four molluscan associations occur in the Nadachi Formation; Acila-Portlandia (lower sublittoral zone), Nuculana (lower sublittoral to bathyal zone), Delectopecten (bathyal zone) and Calyptogena (bathyal zone) associations. The first association also occurs in the Tanihama Formation and the last is recognized in the Kawazume Formation. These associations include rich protobranch bivalves more than those in shallower waters. The lower sublittoral association shows a higher species diversity than the bathyal one.